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DOI	10.1016/j.epsl.2020.116243
	Using thermo-mechanical models of subduction to constrain effective mantle viscosity
	Garel F.; Thoraval C.; Tommasi A.; Demouchy S.; Davies D.R.
发表日期	2020
ISSN	0012821X
卷号	539
英文摘要	Mantle convection and plate dynamics transfer and deform solid material on scales of hundreds to thousands of km. However, viscoplastic deformation of rocks arises from motions of defects at sub-crystal scale, such as vacancies or dislocations. In this study, results from numerical experiments of dislocation dynamics in olivine for temperatures and stresses relevant for both lithospheric and asthenospheric mantle (800–1700 K and 50–500 MPa; Gouriet et al., 2019) are used to derive three sigmoid parameterizations (erf, tanh, algebraic), which express stress evolution as a function of temperature and strain rate. The three parameterizations fit well the results of dislocation dynamics models and may be easily incorporated into geodynamical models. Here, they are used in an upper mantle thermo-mechanical model of subduction, in association with diffusion creep and pseudo-brittle flow laws. Simulations using different dislocation creep parameterizations exhibit distinct dynamics, from unrealistically fast-sinking slabs in the erf case to very slowly-sinking slabs in the algebraic case. These differences could not have been predicted a priori from comparison with experimentally determined mechanical data, since they principally arise from feedbacks between slab sinking velocity, temperature, drag, and buoyancy, which are controlled by the strain rate dependence of the effective asthenosphere viscosity. Comparison of model predictions to geophysical observations and to upper-mantle viscosity inferred from glacial isostatic adjustment shows that the tanh parameterization best fits both crystal-scale and Earth-scale constraints. However, the parameterization of diffusion creep is also important for subduction bulk dynamics since it sets the viscosity of slowly deforming domains in the convecting mantle. Within the range of uncertainties of experimental data and, most importantly, of the actual rheological parameters prevailing in the upper mantle (e.g. grain size, chemistry), viscosity enabling realistic mantle properties and plate dynamics may be reproduced by several combinations of parameterizations for different deformation mechanisms. Deriving mantle rheology cannot therefore rely solely on the extrapolation of semi-empirical flow laws. The present study shows that thermo-mechanical models of plate and mantle dynamics can be used to constrain the effective rheology of Earth's mantle in the presence of multiple deformation mechanisms. © 2020 Elsevier B.V.
关键词	dislocation creep mantle viscosity olivine rheology parameterization subduction dynamics thermo-mechanical numerical modeling
英文关键词	Algebra; Creep; Crystals; Dynamics; Elasticity; Fits and tolerances; Mechanisms; Silicate minerals; Strain rate; Structural geology; Viscosity; Dislocation dynamics models; Geophysical observations; Glacial Isostatic Adjustments; Slab sinking velocities; Strain rate dependence; Thermomechanical model; Upper mantle viscosity; Viscoplastic deformation; Parameterization; deformation mechanism; dislocation; mantle convection; model; olivine; parameterization; strain rate; stress; subduction; temperature; thermomechanics; upper mantle; viscosity
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202599
作者单位	Géosciences Montpellier, Univ. Montpellier, CNRS, Montpellier, France; Research School of Earth Sciences, The Australian National University, Canberra, Australia
推荐引用方式 GB/T 7714	Garel F.,Thoraval C.,Tommasi A.,et al. Using thermo-mechanical models of subduction to constrain effective mantle viscosity[J],2020,539.
APA	Garel F.,Thoraval C.,Tommasi A.,Demouchy S.,&Davies D.R..(2020).Using thermo-mechanical models of subduction to constrain effective mantle viscosity.Earth and Planetary Science Letters,539.
MLA	Garel F.,et al."Using thermo-mechanical models of subduction to constrain effective mantle viscosity".Earth and Planetary Science Letters 539(2020).